Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
H,W=map(int,input().split())
L=["#"*(W+2)]
n=0
for i in range(H):
  S=input()
  n+=S.count(".")
  L.append("#"+S+"#")
L.append("#"*(W+2))
r=[(1,1)]
dic={(1,1):1}
m=[(1,1)]
i=1
mm=[]
nyan=[(0,1),(0,-1),(1,0),(-1,0)]
while m:
  i+=1
  for a,b in m:
    for c,d in nyan:
      x,y=a+c,b+d
      if L[x][y]=="." and (x,y) not in r:
        r.append((x,y))
        mm.append((x,y))
        dic[(x,y)]=i
  m=mm[:]
  mm=[]
if (H,W) in r:
  print(n-dic[(H,W)])
else:
  print(-1)